The invention relates to a method for eliminating the solid constituents (particles) contained in the exhaust of internal combustion engines equipped with fuel feed means, in particular Diesel engines, and to a device for practicing the method.
To reduce the particle emission of internal combustion engines, in particular Diesel engines, filters are generally employed, which consist of, for example porous ceramic materials or steel wool fabrics. These filters will retain the particles entrained in the exhaust, in particular carbon particles and other incompletely burned hydrocarbons, from a certain particle size on. To prevent clogging of the filter and the consequent risk of putting the engine out of commission, these filters must be regenerated from time to time. The regeneration is accomplished as a rule by combustion of the accumulated combustible particles, and is triggered by attainment, spontaneous or controlled, of an exhaust temperature required for such a combustion.
However, combustion of the particles accumulated in the filter can take place only if the exhaust has an oxygen concentration of at least about 3 to 5%. But the oxygen content in the exhaust of Diesel engines, in particular of suction type engines, is often distinctly below these values in the full-load range. The consequence is that despite high exhaust temperatures, the particles collected in the filter cannot burn, and the exahust back-pressure therefore rises. This exhaust back-pressure rise in turn leads to a reduction of the air throughput and hence, since the fuel feed means associated with the engine continues to deliver a fuel flow adapted to the load demand, to a further decline of oxygen content in the exhaust and a further intensified carbon emission of the engine. So the filter gradually clogs, and the power output declines very rapidly, until the engine comes to a stop and cannot be restarted.